Abstract: Aboveground parts of Astragalus strictus distributed in the Tibet autonomous region, was used to prepare aqueous extracts to test the allelopathic effects on Avena sativa, Amaranthus retroflexus, Trifolium repens and Capsella bursa-pastoris using Petridishs with filter papers. Allelopathic effects of aqueous extract were tested on seed germination, root length, seedling height and fresh weight of four species of Astragalus. The malondialdehyde (MDA) content, and the activities of superoxide dismutase (SOD), and peroxidase (POD) of A. sativa and T. repens were investigated to reveal the allelopathic potential of A. strictus, and thereby to provide a theoretical basis for further development and use of A. strictus resources. The aqueous extract inhibited seed germination and seedling growth of A. sativa, and the inhibition was enhanced with an increase in extract concentration. Seed germination of A. retroflexus, T. repens and C. bursa-pastoris were also inhibited by the aqueous extract, and the effects on seedling growth presented an obvious ‘concentration effect’, promoting growth at the lower concentrations and inhibiting growth at the higher ones. A. retroflexus seed germination was inhibited completely when the aqueous extract concentration was 100 mg/mL. The activities of SOD, POD and MDA contents of A. sativa and T. repens were affected by different concentrations of aqueous extract. SOD, POD activities and MDA content markedly increased at 50 mg/mL aqueous extract, whereas at 100 mg/mL, the extract increased MDA content and reduced the enzyme activity in the seedlings of A. sativa and T. repens. Therefore, A. strictus shows a great allelopathic potential.